Shortwave Infrared Upconversion Imaging with Tunable Dual-Resonance Microcavity.

Yu, Kangning; Kottilil, Dileep; Liang, Liangliang; Tjiptoharsono, Febiana; Pei, Peng; Zhang, Yuxiang; Wu, Yao; He, Qian et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

Shortwave infrared (SWIR) imaging is widely employed in light detection and ranging, biomedical imaging, industrial inspection, and night vision. However, current InGaAs-based SWIR cameras remain expensive due to their complex fabrication and cooling requirements. Here, we report a cost-effective alternative using a standard silicon camera, augmented by upconversion from NaYF<sub>4</sub>:Er@NaYF<sub>4</sub> core-shell nanoparticles in a tunable, dual-resonance Fabry-Pérot cavity. A spatially varying cavity length allows spectral tunability, and the dual-resonance design enhances infrared absorption and visible emission simultaneously, resulting in up to 10<sup>4</sup>-fold increase in upconversion intensity over a broad range of excitation wavelengths (1530-1570 nm). This enhancement enables imaging at 1550 nm with sub-10 μm spatial resolution, comparable to InGaAs-based systems, but at a significantly lower cost. We further demonstrate the potential of this platform for silicon wafer alignment and low-visibility imaging. This work introduces a scalable, cost-effective approach for SWIR imaging by leveraging mature silicon technologies and cavity-enhanced photon upconversion.